Metal frame rheostat



Sept 15, 1931 =N. c. scHELLENGER A1,823,472

METAL FRAME RHEOSTAT Filed June 7, 192

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f .50 @im man@ Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE y NEWTON C. SCHELLENGER, OF ELKHART, INDIANA, ASSIGNOB T0 CHICAGO TELEPHONE l SUPPLY COMPANY, 0F ELKHART, INDIANA, A O ORPORATION OF DELAWARE METAL FRAME RHEOSTAT Application med :une 7, 1926. serial N6. 114,126.

My invention in general pertains to elec'- trical apparatus and more particularly to electrical current controlling apparatus such 1 the winding as rheostats and potentiometers.

In the operation of conventional rheostats and the like it is necessary to move the rheo- Stat arm`over an objectional hump or raised portion when moving it from the olf position onto the winding. That is to say, on account of the winding being disposed on the edge of thestrip' or core it is necessary in moving the arni from the off position onto that the arm be raised or forced Vthereon from theedge of the strip. Obviously, such a feature does not permit of a highly smooth and uniform movement on the part of the contact arm and in addition is deleterious to the longevity of the arm itself.

I propose to and compact r eostat wherein a few turns of the resistancewire are buried, so to speak, in the insulator core or Winding stri sullciently deep so.that the contact sur ace of these Windin s'will be flush with the adjacent edge o the insulator strip, thus enabling the arm to be moved freelyto and from an-o' position and onto the windings without it having to strike hump or raised portion.

In general the rheostat or potentiometer or over-ride a strip above referred to may be wound in ac-V c ordance with the .method disclosed and claimed in the co-pending patent applicationof Charles Havlish, Serial No. 729,479, filed August 1, 1924. The primary distinction between my present resistance strip or core and that illustrated in the `co-pending application resides in the fact that I provide a notch in the edge of'one end of the strip so that the last few windings may lie in this notch and be flush with the adjacent Yedge of the strip. The strip is first preferably completely wound in accordance with the method disclosed in 'the co-pendlng patent application. Then the last few windings are taken off or removed up to the. notch. In other words, after the strip is wound I preferably sever the last several turns following the notch. This method of manufacture provide a simple, inexpensive -strlp the same assures that the windings in the notch will' l to the positioning of an insulating strlp inter-l mediate the body and the resistance strip. This insulating strip has a castellated edge for insulating the turns on vthe Strip from the body or yfframe.

By castellating the edge of the insulating is enabled to more properly seat or adjust itself on the flange of the body. Also, this castellated strip will not be damaged or broken very easily when being mounted on the body as is the case with analogous strips which have not been castellated.

In 'accordance invention I form or punch spaced prongs from the conc-ave portion of the'hollow metallic frame which prongs lserve as stops for limiting the movement of the contact arm.

The contact arm of my improved current controller is.provided with a resilient integral mounting preferably a hub adapted to be secured to an end of the operating shaft .-or rod of the controller.

Other objects and advantages of my in# vention will more fully appear from the following detailed description taken' in connec-` Figure 3 is a detail view of my novel contact arm assembly;

with other` features of my Figure 4 is a side view of the contact arm assembly illustrated in Figure 3;

Figure 5 is a sectional view taken on substantially the line 5-5 of Figure 2 and drawn to a somewhat enlarged scale; Figure 6 in a detail view illustrating the resilient washer adapted to be associated with my novel contact arm;

, Figure 7 is a, fragmentary view of the n notched end of the insulating strip and the windings thereon; Figure 8 isa fragmentary view partl in section'illustrating the castellated edge o the infsulator and taken on substantially the line u; 8-8 of Figure 2;

Figure 9 is a. fragmentary view somewhat similar to Figure 1 illustrating a poten- .l tiometerembodying the features of my 'mvention; and

go Figure 10 is a fragmentary sectional view taken o n substantially the line 10T-10 of Figure 9 looking in the direction indicated by the arrows. 4 f' Referring now to the drawings in detail in g5 which like reference numerals designate simi lar parts throughout the several views, 2 0

denotes generally a metallic frame of a cur- The concave portion 22 is provided with an annular opening 23, disposed in a substantialy ly central position. That is to'say,'this openingl23is concentric with'the body 20. Also formed integral with the concave portion` 22 area pair of prongs 24 and 25 which constitute stops and whose purpose will be more fully explained hereinafter. /These prongs 24 and 25 are preferably punched from the portion 22 leaving apertures 26 land 27 respectively in' the ortion 22 (Fig. 1). y l Associated wit the body `20 is a sleeve or tubularelement 28 having a reduced end 29 which extends throughthe opening 23 Ain the concave portion 22. This sleeve 28 is se.-l cured to the concave portion 22 by the turnedbackportion 30 which may be formed by any conventional riveting a paratus or the like.

In other'WOrdS, the en of the reduced portion 23 of the sleeve 28 is Ain reality spread out over the surface of the concave portion ,22 to clench the sleeve thereto. It should .be observed that the concave portion 22 is provided at its'centerv with a substantially iatr portion 31. to which the end of the sleeve 28 is riveted, so to speak.

Thebore 32 of the, sleeve 28A is threaded .also be noted that the annular ange 21 is adapted to abut the surface of theypanel 35; In other words, the end of the Bange 21 is in linewith the end of the sleeve'28 asis obvious in Fig. 2.

Extending through the telescoping sleeves 28 and 33 is an operating shaft 36. Secured to the external end of this'shaft 36 is a han- 85 dle or knob 37 by means of which the shaftl may be actuated. The. shaft 36 is journaled in the bore 37 of the sleeve 33 and in the reduced bore 38 of the reducedportion 29 of the sleeve 28. The shaft 36 is provided .with 90 a reduced end 39 and a shoulder 40 which abuts the reduced portion .29 of the sleeve 28. -Mounted upon the reduced end 39 of the shaft 36 is a kresilient washer 41 such as that illustrated in Fig. 6. The edge of this wash-` er is castellated as indicated at The Washer as shown in Fig. 3 .is arcuate in shape and has an Aedge which engages the flat portion 31 associated with theconcave portion 22'in the body 20. This Washer serves two` 100 purposes, as will be tion to hereinafter follow.

Also mounted upon the reduced porti0n39 1 is a contact arma'ssembly 45 such as.that illustrated in detail in Figs. 3 and 4. This 105 assembly includes" a contact arm 46 having` an arcuate shaped Ymounting portion :47. The base `or Imounting portion 47 is provided with an arcuate slot 48, as best illustrated in Figs. 1 and The base is' also provided no.

with an oifsetportion 49 which is adapted to be iexed into the plane of the mounting or A base 47 as will become more apparent hereinafter. The contact arm 46 and its base 47 may be made of any suitable material such,

for example, as nickel, silver, or the like.

The Contact arm46 includes a slanting portion 51 and a substantially-flat contact port1on`50.' Mounted onthe offset portion 49 is a collar or hub 52 having a bore 53 adapt- 12e)v ed t0 receive the end 39 `ofthe shaft 36. .The collar 52 has formed integral therewith a reducedportion 54 which extends through an opening-55 in the offset portion 49 and isV clenched. to the offset portion 49 as indicated 125 at 56 in Fig. 2.

Y When the assembly 45 vis removed from the g end 39 of the shaft 36 the hub 52 and the 'portion 49 will assume the position illustrated in Fig. 4. However, when the assembly 45 139 obvious from the descripis mounted upon the shaft the portion 49 will mounting for the 4the wire is wound in the be flexed into the same plane as the rest of the mounting or base 48 of the contact arm 46. This will result in the contact portion 50 of the arm 46' being resiliently urged into engagement with the resistance wire or windings designated generally by the reference character 60. The collar 52 is provided with a set screw 61 by means of which the same may be fastened to the end 39. of the shaft.

Now the assembly 45 is mounted on the end 39 abutting the resilient washer 41. This washer 41 not only serves as a resilient assembly but-also serves as a universal mounting due to its arcuate shape. This arrangement secures a. smooth movement on the part of the contact arm throughout its range of movement. Also, it should be observed that with the exception of the contact portion` 5() the entire contact arm assembly 45 is disposed in the depressed portion 22 within the dimensions of the body 20, thus resulting in a very compact piece of electrical apparatus.

The resistance windings previously referred to are wound upon an insulator or core 62 in accordance with the winding process disclosed in the co-pending patent application of Charles Havlish, Serial No. 729,479, filed August 1, 1924. The primary difference between the strip 62 that I employ and that disclosed in the co-pending patent application lies in the fact that I provide one end of the strip with a notch such as that desl nated bythe reference character 63 in Fi The strip is wound from one end to the ot er, and thereafter I preferably sever the last few turns-on the end of the strip after the notch hat is to say I remove the turns on this end of the strip 62 up to the notch. By winding over the notch initially I find that the unwound `portion desi ated by the reference character 65 in Figs. nand 1 constitutes the off portion of the rheostat.

he strips 62 are wound by the same being revolved through a threaded nut as disclosed in the co-pending patent application. The threaded n ut cuts into the edges of fibre thereby feeding it forward at a uniform rate and grooves made by the nut. This method of winding is an unusually cheap and eicient way of placing I wire on the strip. The notch 63 is employed for burying the first few windings 60 so that they `will be flush with the-edge of the strip or core 62. This enables the end of the contact arm to be moved from the off position onto the windings without having to strike an objectionable hump as is the case with practically all other rheostats now on the market. It will be observed from Fig. 7 thatthe windings in the notch 6 3 are buried to or raised portion.

with the top edge such an extent that their top surface is iush with the edge of the strip 62.

into an arcuate shape and disposed about the periphery of the body 20. Positioned intermediate the wound strip 62 and the periphery of the body 20 is an annular insulating strip which may be made ofany suitable insulating material. This strip 7 O has an annular.-

flange 71 adapted to lit over the flange 21 of the body 20. The flange 7l is preferably castellated as indicated at 72 in Fig. 8. This enables the insulating strip 70 to be snugly positioned intermediate the body and the Wound strip 62. By castellating the flange 71 it is not necessary to break or damage this flange 71 adapted to fit overthe flange 21 of the body. Also the flange 71 serves to insulate the bottom of the windings on the stri 62 from the metallic flange 21 of the body 20. The two strips 62 and 70 are tightly drawn around the periphery of the body 20 and are secured at opposite ends to the body adjacent the prongs or stops 24 and 25 as will now be described in detail.

Referring to Fig. 5, it will be seen that each end of the winding strip 62 and the associated end of the strip 70 is secured to the wall of the body 20 adjacent one of the two prongs. One end of the winding strip 62 is secured t0 the frame 20 by means of a bolt 75 having a washer 76 and an insulating washer 77 disposed about its shank. The washer 77 abuts the inner wall of the casing 20 and serves to insulate the bolt 7 5 from the body. The winding 60 on the strip 62 is connected to this bolt and held in place by means of a washer 78. The washer 78 is maintained in place by a pair of lock nuts 79 and 80.

The other end of the strip 62 is secured to the wall of the frame 20 by means of a bolt 81 and a pair/of lock nuts 82 and 83. I preferably dispose a washer 84 intermediate the strip 62 and the lock nut 82 as shown in Fig. 5. It will be obvious from the foregoing'description that the frame 20 is connected to the contact bolt or post 81 and one end of the winding is connected to the contact bolt or post 75 which post is insulated from the frame by means of an insulating washer 77 previously described. The circuit is completed through the means of tHe movable contact arm 46.

The end 50 of this arm 6, as previously described,` is resiliently urged into engagement with the exposed edge of the windings 60 on the strip 62. As previously described, the contact arm is adapted to bemoved the off portion 65 of the strip 62 onto the adjacent winding without striking any hump the fact that the lirst few windings are flush of the insulated strip 62. 10, I have illustrated my toa "potentiometer, The

In Figs. 9 and invention applied from This is possiblel due to After the strip 62 has been wound it is bent Y that the present invention is not to be limitv'as primary vdifference between this device and that described in connection with Figs. 1 to 8 inclusive, resides in the provision of three terminals or bindingv posts instead of two.

In this modification of the invention, the

4posts or bolts 7 5 and 81 are both insulated lfrom the frame by means ofl washers such as the insulating washer 7 6 shown in (Fig. 5. The opposite ends of the windings jio 60, on the strip 62' are securedto lthese two bolts 75 and 81 Ain a manner well known to those familiar withfthe potentiometer art.

Positioned intermediate the two binding posts75 and 81 is an additional terminal 90 which is originally secured to the concave' portion 22d of the metallic frame 20 by means of a bolt 91 and lock nuts 92 and 93. Thus it will be seen that my invention c an be readily applied to both rheostats and potentiometers. Of course,it,is to'be understood ed in its application to these two forms of electrical apparatus but only insofar as defined spirit of the appendedby'` the scope and claims.

I claim '1. Aresistance strip for use in current controllers having"v a sliding contact, said resistance comprising a' strip of insulating material having a notch in a portion thereof and wire turns each 'extending across the front and the rear of said strip, the said notch being adapted to receive a turn to cause the' exposed surface of said turn to be-ush with an adjacent bare surface of said strip, said bare surface being adapted to 'serve as the olf point for the sliding contact.

' l2. In an electrical current controlling device, a frame, contact mechamsm assoclated therewith including a contact arm, and a* resistance strip associated with said frame and cooperable with said contact arm,.said strip including an insulator core having a plurality of wire turns thereon', each extending across the front and therear of the core, the turn adjacent the olf point of said contact arm being buried in the strip with its exposed surface Hush with the adjacent exposed edge ofthe insulator strip.

3; In an electrical current control device, a substantiallycylindrical hollow body com- ,f prising a circular metallic shell having a conv i cave vshaped end, a resistance associated with the periphery of said shell, contact mechanism connected to the concave shaped end including a contact arm cooperable with said resistance, and 'means for limiting the move- Y ment of said arm including a stop consisting of la prong extending laterally from and integral with said concave shaped end.

4. In an electrical current control device,

a substantially cylindrical metallic body having a concave shaped portion `at one end, the

mit said baai: whe he other `end having a peripliealhlgpnge to pierig y agams a mounting panel, a resistance strip disposed about the periphery ofsaid body, an insulator intermediate the said resistance vstrip and the -body and contact mechanism associated with the concave portion vand disposed substantially within the length of the body including a contact arm adapted to cooperate with the said resistance strip.

5. In an electrical current control device, a substantially cylindrical hollow body comprising a circular metallic shell having a concave shaped'end, the other end of said body having a peripheral iange adapted to fit against'a mounting panel, a resistance associated with the periphery of said shell, and contact mechanism lconnected to the concave [end and disposed substantially within the overall length of the said shell including .-1

a contact arm cooperable with said resistance.

6. In an electrical current control device, a metallic frame comprising a substantially cylindrical hollow body having a concave shaped end, said body having a lateral flange s said contact mechanism beingconnected to the said concave shaped end.

7. In an electrical current control device, a metallic frame comprising a substantially cylindrical hollow body having a concave shaped end, said body having a lateral flange associated with its periphery, a resistance strip disposed about the periphe ofthe bodywith an edge adjacent said lmgm-an insulator intermediate said body and said Aresistance strip, said insulator having alati eral extension adapted to lie over said flangeV to insulate it from. said resistance strip, a contact arm cooperable with the said resistance strip disposed substantially Within the length of said cylindrical body, said arm being connected to said concave shaped vendv and having a portion adapted to. engage an end of the said resistance strip, and means' for limiting the movement of the arm comprising a stop consisting of a prong'integral wih and punched from said concave shap en 8. In an electrical current control device, Y ametallic frame comprising a substantially cylindrical hollow body havmg a concave i' shaped end, said body having a lateral flange associated with, its periphery, a lresistance strip' disposed about the periphery of the body with'an edge adjacentl said liange, an

'insulator intermediate said body' and said resistancel strip, lsaid insulator having a lateral extension adapted to lie over said flange to insulate it from said resistance strip, a Contact arm cooperable with the said resistance strip disposed substantiallywithin the length of said cylindrical body, said arm being connected to said concave shaped end and having a portion adaptedpto en age an edge of the said resistance strip, an means i for actuating thesaid arm, said resistance strip comprising a lngs onan insulator core, the winding adj acent the` off point of said contact arm being buried in the strip with its exposed surface flush with the adjacent exposed edge of the insulator core.

9. A resistance device for current controllers comprising a strip of insulating material, a resistance wire wound upon the strip, saidl strip` being cut away from one edge atan inclination. downwardly toward the adjacent end of the strip providing a notch decreasing in depth away from said adjacent end of said strip, the terminal coil of the wire being disposed at the deepest portion of the notch with its upper portion substantially flush with the upper face of the strip.

10. A resistance device comprising, a thin Hat strip of insulating material, and a resistance wire wound upon the strip, said strip having a notch in one edge and adjacent one end, said notch receiving the terminal winding of the wire and the contact face of said terminal winding being substantially flushwith said edge of the strip.

l11.. In combination, a contact arm, an insulating strip disposed in edgewise relation tothe arm and provided with a notch in its edge overwhich the arm operates, and a resistance wire wound upon the strip for contact by the arm, the terminal winding of the wire lying in' said notch and having its contact face substantially flush with the edge of the strip.

12.-In an electric current control device, a metallic body comprising a rim and a concave end, a resistance disposed in insulated relation about said rim, Aa pair of insulated fastening mem ers serving as terminals for fastening the ends of the resistance to the said rim,

contact arm cooperable with the said resistance, and a third terminal riveted to the said my name this 26th day of concave part of the metallic body.

In witness whereof, I hereunto subscribe May, 1926. NEWTON C. SCHELLENGER.

plurality of wireI windl contact mechanism associated with the concave end of the body includin a Y 

